High School Biology-Chemistry SMILE Meeting
09 October 2001
Notes Prepared by Porter Johnson

Barbara Pawela (May School, retired)Barbara showed some plants just taken from her yard [or
"garden", if you speak British], as well as those obtained
elsewhere We investigated the structure, life cycle, and process
of reproduction for the following plants:

Staple three edges of the towel to the bag. Seal the top of
the bag and hang it, adding small amounts of water to keep the seeds
from drying out.

Check the seeds each day. When the roots are about 4 cm long,
remove the seeds and examine the roots with a hand lens. Draw what you
see.

What did you learn?
How can you use what you learned?

Q: What do root hairs look like?A: Root hairs are very fine hairs sticking out of the
root.

Q: Why do plants have root hairs?A: Root hairs help the plant absorb water from the soil
surrounding the plant.

Q: Do plants that live in water need root hairs?
Explain.A: No. Plants that grow in water do not need root hairs
because they can absorb enough water directly through their roots.

Barbara also showed us tomatoes, walnuts, and eggplants, as well
as seeds of dried flowers --- all taken from her garden as additional
specimens.

Barbara also handed out bean seeds to be grown in the
zip-lock bags. The marigold and pumpkin seeds should be placed in
potting soil to make the plants. We will wait and watch for them
to grow!

Marva Anyanwu (Lincoln Park HS) The Tensile Strength of Spaghetti
(handout)
The handout explained that "raw spaghetti" is a surprisingly strong
material --- before you cook it. Spaghetti***
is categorized by thickness of the strands. In particular, angel
hair spaghetti is thin, and "regular spaghetti" is described as #8
on the boxes.

Tensile strength is measured by stretching an
object until it breaks. A rope used in a tug-of-war is under
tension. Compression occurs when forces push into an
object. For example, a pillar supporting a building is subject to compression.
When a long, thin object is supported horizontally at its ends and
pushed down at the middle, the top edge is under compression
and the bottom edge is under tension.

To measure the tensile (tension) strength of a length of
spaghetti, you can bend it by adding weight to its center until it
breaks. Support opposite ends of a single piece of spaghetti,
allowing 2 cm of each end to rest on the support. Hold
those ends in place so that the spaghetti cannot move.

We worked in groups, using both "thick" and "thin" spaghetti. We
placed a spaghetti strand with the ends on two desks, and over
the strand we looped a piece of string that was tied to a Styrofoam™
cup. We added weights to the cup until the spaghetti strand
broke, and recorded the data. We drew the following conclusions:

Variations in the technique for adding weights could produce
variable results. For example, the results were different when we
dropped weights into the cups, as opposed to placing them inside more
gently. Spaghetti of the same size from different manufacturers
could also yield different results
.

Three of the four groups found that a thin (angel hair)
spaghetti strand was stronger than a regular (#8) strand.

We tested the hypothesis as to whether two pieces of
spaghetti would hold twice as much weight as one piece,
and found that it was false! There may have been problems in
alignment of the pieces of spaghetti, so that they would share the load
equally.

Marva mentioned that she was particularly interested in the SMILE
Biology-Chemistry class. She hadn't thought of spaghetti as being
strong, and was surprised by the experiments.

*** The word spaghetti means little strings
in Italian and is always plural. The rumor that spaghetti plants grow
in long thin patches between lanes on interstate highways is false.
After all, spaghetti requires a hot, dark environment for
proper development.